A multidisciplinary study has highlighted how some traces of the 2015 eruption of the Sicilian volcano were "visible" even in the high atmosphere, hundreds of kilometers from the crater
The energy released during Etna's eruptions is capable not only of shaking the ground and filling the air with gas and volcanic ash, but also of disturbing the ionosphere., hundreds of kilometers high. This is what emerges from the study “Ionospheric Disturbances During the 4 December 2015, Mt. Etna Eruption” recently published in the international journal 'Earth and Space Science', which documents for the first time, in unprecedented detail, the ionospheric disturbances generated by a large lava fountain that occurred on Mount Etna on December 4, 2015.
The study, conducted by a team of researchers from theNational Institute of Geophysics and Volcanology (INGV) and Universities of Trento, Catania, Calabria, and Sapienza University of Rome, In collaboration with the 'Institute of Atmospheric Physics in Prague, used a dense network of over 200 GNSS receivers (Global Navigation Satellite System) installed in Sicily and Southern Italy. The researchers detected slight but evident variations in the ionospheric total electron content (TEC), which appeared between 20 and 30 minutes after the onset of the eruption of 2015 and coinciding with the growth of the eruptive column up to 13 kilometers in height.
"We have demonstrated that even a 'local' and non-catastrophic eruption like that of Etna leaves a trace in space, which can be detected thanks to a dense network of sensors.", explains Federico Ferrara, a PhD student at the University of Trento who carries out his research at the INGV Etna Observatory and first author of the study. “This means that ionospheric observations can also complement traditional volcanic monitoring, opening up new perspectives that were unthinkable until a few years ago.”.
The observed anomalies showed periodic oscillations of 15–25 minutes, propagating up to 200 kilometers southwest of the volcano: signals consistent with so-called “atmospheric gravity waves,” or oscillations of the air propagating in the atmosphere generated by the rapid rise of the eruption column.
To underline the importance of the result is also Michela Ravanelli, of Sapienza University of Rome, co-author of the article: Working with such rich data has allowed us to identify very weak but significant oscillations. This is an important step towards integrating volcanology and space science. Imagining that an eruption of Etna could 'talk' to the ionosphere reminds us how interconnected the solid Earth and the atmosphere are: it's a scientific challenge, but also a great opportunity to improve early warning systems..
“Our work has shown how monitoring networks prove useful well beyond the purposes for which they were initially designed.”, he adds Alexander Bonforte, Senior Researcher at INGV and co-author of the research. The range of applications and the use of the data provided are often surprising, as are the results obtained, which offer new insights and open up new avenues for research. Instruments installed to study and monitor the dynamics of the lithosphere, and volcanoes in particular, have proven useful for investigating upward perturbations in the atmosphere, providing a unique view of the planet's various layers, from the subsurface to space, for a more complete understanding of volcanic phenomena..
"The work is dedicated to Vincenzo Carbone, a physicist at the University of Calabria, whose scientific contribution played a decisive role in the development of the study.", remember Vincenzo Capparelli of the University of Calabria, co-author of the research. “Internationally recognized for his studies on complex systems and awarded the prestigious Lewis Fry Richardson Medal in 2025, Carbone is remembered by the authors with deep esteem and gratitude.”.
According to the authors, although these signals cannot be interpreted alone as precursors of eruptive events, integrating them with those deriving from other disciplines involved in volcanic monitoring could provide new information on energy releases into the atmosphere from deep within the volcano and on the construction of more detailed eruption scenariosEtna, thanks to its frequent activity and the extensive instrumentation installed for its monitoring, represents a unique natural laboratory for developing innovative methodologies of this kind.
The multidisciplinary approach of this study was inspired by the insights of Professors Giovanni Occhipinti and Vincenzo Carbone, experts in ionospheric seismology and complex systems, respectively. The authors dedicate this research to the memory of these two internationally renowned scientists.
Figure 1: Image representing the phenomenon studied. The explosive eruption releases energy into the atmosphere in the form of gravitational-acoustic waves, which, amplified upward, can reach the ionosphere, causing variations in its electron content. These electronic variations are recorded by satellite signals continuously acquired by the network of ground-based receivers. 
Figure 2: A frame from the surveillance cameras of the INGV Etna Observatory in Catania which captures the eruptive column of 4 December 2015
